Increasing the vaporization of fuels can greatly improve the efficiency of internal combustion engines. This can also improve the cold-starting characteristics of engines using fuels such as ethanol and diesel fuel. To this end, many different assemblies have been devised for pre-heating either the fuel, the air or the fuel-air mixture upstream of the engine's combustion cylinder. The typical assembly includes some type of heat exchanger for heating the fluid as it passes through, over or around the heat exchanger and some type of heating means for heating the heat exchanger. Ideally, it is desirable to provide a heat exchanger having a very high surface area for heating the fluid thoroughly as the fluid passes the heat exchanger. U.S. Pat. Nos. 5,054,458 to Wechem et al; 5,086,747 to Curhan, 4,212,275 to Inoue and 5,078,115 to Yamashita et al. all disclose heat exchangers which are honeycomb or otherwise porous to provide a high surface area for heating. For example, U.S. Pat. No. 4,212,275 to Inoue discloses a porous ceramic heater having up to 100 open cells per cubic inch. Now, new technologies allow for the heating surface area of heat exchangers to be increased dramatically beyond what is disclosed in the prior art.